Analyzing VMT Tools for California’s Climate Goals

Despite California’s ambitious target to achieve carbon neutrality by 2045, the state is not reducing greenhouse gas (GHG) emissions from personal vehicle travel, and per capita Vehicle Miles Traveled (VMT) and GHG emissions continue to increase. One challenge is the lack of consistent methods to measure the VMT impacts of transportation projects. New Mineta Transportation Institute (MTI) research, Consistent VMT Mapping and Modeling in California: How Can We Better Assess the VMT Impacts of State and Local Transportation Projects?, uses both qualitative and quantitative data, to answer the question: “What are the advantages and limitations of existing VMT calculators to determine the climate impacts of transportation projects to help meet California’s climate goals?” 

The study divided the evaluation of VMT impacts into two main steps: 1) qualitative analysis of the advantages and limitations of the existing VMT mapping and modeling tool, which included expert interviews, and 2) quantitative analysis of VMT mapping and modeling tools.

Findings indicate that the consistency, contextual relevance, complexity, data accuracy, and user-friendliness of the VMT tools vary significantly based on their design and methodology, and each tool presents a set of limitations and advantages, making it suitable for a specific use or context but not necessarily for another. Recommendations for the state include the following:

• Improve access to accurate, validated data for creating and inputting into VMT models and tools;

• Help create context-sensitive VMT tools capable of capturing local context and change over time;

• Strengthen dialogue between jurisdictions to share information and tools; and

• Encourage using an integrated approach to VMT analysis—which often combines the use of different tools and datasets for various stages of decision-making and scenario planning.

“Potential for exploitation or loopholes exists in some of the VMT tools,” explain the study’s authors. “For example, the NCST Induced Travel Calculator might potentially produce misleading results due to its conservative estimates and fixed elasticity values. In contrast, VisionEval minimizes loopholes through its detailed and comprehensive scenario analysis, though its complexity could lead to misinterpretation of the findings. Users need to fully understand these tools so they can choose the best one for their specific needs.”

This research demonstrates that each VMT tool has its own strengths and weaknesses. By understanding the consistency, context of use, data usage, complexity, ease of use, and potential for misuse or misinterpretation of these tools, policymakers and planners can choose the best tool for their needs and ensure accurate VMT assessments to help California meet its climate goals.

ABOUT THE MINETA TRANSPORTATION INSTITUTE

At the Mineta Transportation Institute (MTI) at San Jose State University (SJSU) our mission is to increase mobility for all by improving the safety, efficiency, accessibility, and convenience of our nations’ transportation system. Through research, education, workforce development and technology transfer, we help create a connected world. Founded in 1991, MTI is a university transportation center funded by the US Department of Transportation, the California Department of Transportation, and public and private grants, including those made available by the Road Repair and Accountability Act of 2017 (SB1). MTI is affiliated with SJSU’s Lucas College and Graduate School of Business.

ABOUT THE AUTHOR

Dr. Serena Alexander is an Associate Professor of Public Policy and Environmental Engineering at Northeastern University focusing her research on addressing climate change. Dr. Shams Tanvir is an Assistant Professor at the California State University, Long Beach focusing his research on sustainable mobility. Syed Tanvir Ahmed and Annie Jones are graduate students in the California State University system.

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